We propose to purify and characterize an antigenically and chemically distinct type of collagen which we believe to be associated with the normal human fibroblast membranes. We have confirmed previous observations that the hydroxylysine content of the bones from patients with Osteogenesis Imperfecta is greater than twice normal. We will attempt to utilize this observation to elevate therapy in Osteogenesis Imperfecta, and as a clue to the etiology of this disease. Finally, we are attempting to establish a radioimmunoassay for type I procollagen in order to assess procollagen levels in various biologic fluids in normal and collagen diseases. BIBLIOGRAPHIC REFERENCES: Lichtenstein, J.R., Bauer, E.A. and Uitto, J.: Cleavage of human fibroblast type I procollagen by mammalian collagenase. BBRC 73:665, 1976. Lichtenstein, J.R., Bauer, E.A., Hoyt, R. and Wedner, H.J.: Immunologic characterization of the membrane-bound collagen in normal human fibroblasts. J. Exp. Med. 144:145, 1976.